The ATS sport sedan is a watershed vehicle for Cadillac and a breakthrough that will change the way General Motors develops all its upcoming vehicles.

The engineers who developed the ATS at GM's Warren Tech Center were focused like a laser on the BMW 3-series, the compact that's widely considered the world's best sport sedan.

It was the first time GM had the confidence to tackle the 3-series head on. The CTS that re-established Cadillac as a competitor for the likes of Audi, BMW, Lexus and Mercedes-Benz tried to outflank the 3-series: it was nearly the size of the larger 5-series, but priced like the compact 3-series.

Job 1 was making the car light. Controlling weight is the greatest test of an automaker's discipline, focus and engineering expertise. Nearly all GM's recent vehicles have been heavier than their competition. That put GM at a serious disadvantage for fuel economy, handling and performance.

The ATS shocked the auto industry when it weighed in about 200 pounds lighter than a 3-series. The ATS's fuel economy and performance also compare well to leading established sport sedans.

GM has now enshrined the weight-saving techniques that created the ATS in the development process for its future cars and trucks.

The ATS is also destined to become the heart of Cadillac's model line. It's likely to spin off coupe, convertible and perhaps station wagon models, creating a family that should be Cadillac's best seller around the world.

The ATS pioneers new technologies that none of Cadillac's competitors can match, including safety systems that relay warnings about parking obstacles, inadvertent lane departure, potential collisions and more by subtly vibrating the driver's seat. The system is sure to spawn imitators, as are the excellent voice-recognition and iPad-style controls of CUE, the Cadillac User Experience.

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Second place: Dodge Dart

The 2013 Dart is the best combination of Italian ingredients and American creativity since the Hawaiian pizza. Chrysler engineers and designers adapted the Alfa Romeo Giulietta’s architecture, engines and transmissions to create the roomy and enjoyable compact. The fuel-efficient and advanced sedan gives Chrysler its first legitimate competitor to leaders like the Honda Civic, Ford Focus, Chevrolet Cruze and Hyundai Elantra.

Third place: Chevrolet Malibu and Nissan Altima (tie)

Four good new midsize sedans hit the market this year, and the 2013 Chevrolet Malibu and Nissan Altima are my choice for the best.

The Altima set the competition back on its heels with a 38-m.p.g. highway fuel-economy rating for all its four-cylinder models. Other leading midsize sedans require you to pay extra for special tires, aerodynamics and electric grille shutters for max fuel economy. That’s just one of many winning features in Nissan’s best-seller.

The Malibu is a terrific all-around package. Its European-developed chassis and steering provide good handling and comfortable high-speed cruising. Three engines offer a broad range of performance and fuel consumption. It showcases GM’s new voice-recognition and touch-screen controls, which may be the industry’s best.